What multiuser serial subds do you know?

Question

Database

On this site I found multi-user subds with serial and parallel access in the classification.
I can not understand how a multi-user subd can be with sequential access - for all authorized users, operations are performed sequentially in turn (essentially with locks) or what?
MySQL or Postgre - is it serial or parallel?
And if they are serial, then which ones are parallel?
I tried google. Something is wrong with Google :(
In MyISAM, for example, several users can read one table at the same time. But when writing it, it is completely blocked. InnoDB also has locks, you can’t get away from them, otherwise ACID will not be observed.

Answer 1

read this better: it
will expand horizons to infinity.
If you really want to get into how the DBMS works - then this is
fallabs.com/tokyocabinet
And so you can assume that SQLIte is of the sequential type, because it is one file. But what you are asking is absolutely useless in practice.

Answer 2

You can get away from locks, and probably many modern databases have left them. I know of two types of transactions (maybe more of them): a locking mechanism and a versioned one. With the first one, I think there are no questions, and the second one is when everyone is allowed to write to the database, but at the same time, a version is indicated for each entry (most likely just a transaction ID). And then, when committing, they indicate one of them - that this transaction is confirmed. Thus, if the select is executed inside a transaction, it sees only the records of its transaction (or previously confirmed ones), if outside the transaction, then only the last confirmed ones.
At first, such a mechanism began to be used in Interbase, then it spread to many industrial databases.
MySQL still uses locks, which causes a lot of problems with triggers and stored procedures. How things are in Postgresql - I do not know.
I don’t know about serial and parallel access - maybe the legs grow from here, or maybe the author of the article came up with something from himself. There was a truth when that a problem in , that whether from one client, whether from one user it was impossible to open more than one transaction. But it seems to depend more on the access driver.

Answer 3

Read about the following:
1) Transaction isolation
2) MVCC
3) Snapshot isolation
And some book on the database. Now you do not understand anything about the operation of a multi-user database.
The site you found is absolutely incredible. Consider looking for other sources.